1. we cannot use averages since it makes the restriction even more complicated (and it's complicated enough already). We want the amounts to be at least a little bit logical (you can now see that the total expenses value is the same as the baseline weekly economy total expense value).
2. I know that we look at the weekly economy as if we're paying the salaries upfront and from that view, you are right, this economy is for the first week of the next season however, strictly looking, the new season hasn't started yet at the time the economy update was run. Long story short, last nights economy update is considered a last update of the old season and the first update (which will not have OT) is the next one, in 6 days.
The reason why we chose that week? It's because that's the first week after promotion/demotion. If a team changes division, the income and expenses change dramatically and OT cannot be based on half of data from it's old division, the other half from new one. We need to have at least one home match and we do have that after 3 matches have been played.
I hope that clears things up and I'm sorry you were mislead. I will change the wording of the OT text to make it more clear which update is OT free though.